Questions on Dosing and Nitrate Uptake by the plants

[shogsten]

I've recently (last week) started dosing ferts and specifically KNO3. I am quite certain I was nitrate limited prior to beginning to dose nitrates. The local water has 0.5pmm phosphate so algae has been a large problem. The problem I am seeing it that the nitrates are being consumed very rapidly. Yesterday I tried an experiment of bringing the levels up to 5pmm over the course of 4 hours. By this morning levels are back to unmeasurable.

My questions

1. Will this uptake slow down as the plants (and algae?) use up the Nitrates ? If it will slow, is there something I should be doing to get to this point ?
2. If the uptake continues at the current rate any ideas of how I can keep a more stable amount of Nitrates in the tank ?
3 How high can I dose nitrates all at once without harming the fish ? Can I put 5-10 ppm into the tank without stressing the fish ?

Dosing - following the PPMD guidelines using Chuck Gadd's calculator and supplies from Greg Watson.

Tank details - 150 gallon
Lighting PC - 4 hours of 200 watts - 1 hour off - 3 hours 400 watts - 1 hour 200 watts
PH 8.0 and stable - tested 48hours out of the well
Nitrate - 0 ppm
Nitrite - 0
Ammonia - 0
GH - 3 degrees
KH - 20 degrees (same as it comes of of the tap)
Phosphate >.5 ppm
Plants - Hornwort (lot's) pruned often - Green Camoba - Luwidgia - Anacharias - Crypts - 2 large Anubias - 2 small sword plants - 2 small vals currently coming back from a complete meltdown
Fish - 10 Serpae Tetras, 8 Black Tetras, 4 Green Cory Cats, 6 Oto's, 7 Silver Tetra's - 1 very old Zebra Danio

No CO2 yet - regulator is ordered


Scott Hogsten

 

[malkore]

Short answer: yes, plants intake will slow down after a bit.

Your plants were basically nitrate starved. Right now they are not only using the nitrate in the water to keep growing, they're also storing their reserves back up.
I'd even dose up to 10ppm during this little phase.

Once you get your CO2 rolling, I think you'll find the algae disappearing more readily. At that point, I'd run all 400 watts most of the day, and you can have a 200watt run as a sunrise/sunset period for 45 mins on either side.

 

[shogsten]

So I should be able to dose up to 10 ppm all at once without stressing out the fish ? Or would I be better to dose a couple of times a day ? Getting the ferts in line does seem to be helping with the algae problem and hopefully my regulator will be here this week and I can get C02 injection going by the weekend.

 

[Mr Burns]

Levels unmeasurable by the next day? Hmm...where have I heard that before? There are some sites that suggest dosing about 1ppm per day to decrease fish stress, but in high light tanks like mine, that 1ppm won't make it to the next day. I'm still testing every day and taking notes on how the tank is using ferts, but it's looking like my NO3 dosing will be ~3ml after a water change to get ~10ppm, and 1ml every morning to maintain. Looking at my notes, this is an estimate that will require more testing and more notes. That said, I wouldn't dose 10ppm all at once. 5ppm in the moring and 5ppm at night would be enough time to allow fish to adjust. Stability comes with testing, observation, and reviewing notes. If you can keep your nitrates in the 5-10 range every day, you'll have it made...then it's on to other nutrients like iron and potassium...

When you start your CO2, introduce it gradually. I went from about 5ppm - 30ppm in a days time and the thread algae exploded on my lutea crypt and similarly (though less severe) on my anubias nana. This should go away once the tank stabilizes again, but there was enough of a disruption that allowed the algae to get ahead.

 

[malkore]

I think people worry too much about adding nitrate. I normally dose 5-10ppm after a water change, and the fish are unphased. Some people even dry dose KNO3 in their tanks, and when I do this, my fish consume the fertilizer granuales. Yet they don't show any signs of illness afterwards.

10ppm is the most I'd suggest dosing at any one time, and right now it's going to help you catch up to the plants needs.